The game was being developed by Edwards' close friend Paul Proctor, who was previously responsible for the BBC Micro conversions of Ultimate Play The Game titles like Sabre Wulf, Alien 8, and Knight Lore and later went to get a job at Rare (the successor to Ultimate) on games like Wizards & Warriors and Pin-Bot.
According to Edwards, Plasma0 is essentially "a sideways scrolling update of Ultimate Play the Game's Jet Pac", which you can see quite clearly in the roughly 1-minute video he shared of the game. In the video, we see an astronaut flying horizontally across an alien planet dodging projectiles and collecting different pieces of a spaceship to make their grand escape.
If you're wondering why it was abandoned, sadly, it doesn't seem like we have a concrete reason. As Edwards explained on Twitter, "None of us can recall the reason for it being abandoned. Paul can't actually remember doing this game!"
After working on this title, Proctor apparently moved on to working on another NES game, which Edwards is also currently trying to recover.
